The present invention relates to a new class of overbased materials and a process for preparing them.
Overbased materials are well known and have been described, for instance, in U.S. Pat. No. 3,492,231, McMillen, Jan. 27, 1970, which discloses a non-Newtonian colloidal disperse system comprising solid, metal-containing colloidal particles dispersed in a liquid dispersing medium and, as an essential third component, at least one organic compound which is soluble in said dispersing medium, the molecules of said organic compound being characterized by a hydrophobic portion and at least one polar substituent. Materials which can be overbased are generally oil-soluble organic acid including phosphorus acids, thiophosphorus acids, sulfur acids, carboxylic acids, thiocarboxylic acids, and the like.
U.S. Pat. No. 2,971,014, Mastin, Feb. 7, 1961, discloses an improved method of incorporating large amount of metal with hydroxy-aromatic compounds to form oil soluble compositions. The process comprises mixing (a) an alkylated monohydroxy aromatic compound, (b) an oil-soluble, metal-free non-tautomeric organic polar compound, and (c) at least two equivalents of a basic inorganic metal compound, then treating with an acidic gas.
U.S. Pat. No. 2,798,852, Wiese et al., Jul. 9, 1957, discloses oil-soluble metal-containing materials, prepared by heating a mixture of (a) a substantially neutral, aliphatic ketone having at least 13 carbon atoms; (b) a monohydric alcohol having a molecular weight less than 150, and (c) a basically reacting inorganic metal compound. The ketone can be an oxidized petroleum fraction. The presence of acidic products is said to be not essential to the successful operation of the method of preparation; it is preferred to use as a starting material an oxidized hydrocarbon which is substantially free from carboxylic acids and their esters. One form of the process includes the step of treating the immediate complex material with a weak: inorganic acidic material such as CO.sub.2.
It has thus been known to prepare overbased materials using as a substrate an oil-soluble acidic material. The acid functionality can be provided by an acid group such as a carboxylic, sulfonic, or phosphonic acid, by aromatic--OH or amine groups, or by other groups exhibiting acidic labile hydrogen character, such as alpha-hydrogen-containing ketones. For some materials, the substrate is not itself acidic, but it is capable of being hydrolyzed under overbasing conditions to form an acidic material. For example, certain esters can be overbased because under overbasing conditions the ester will saponify to form the acid. Each of these acidic materials are normally viewed to exist as an anionic component of a salt, when they are employed as the substrate of an overbased material. The present invention, in contrast, provides overbased organic materials in which the substrate has no appreciable acidic character and thus cannot be neutralized in the usual sense by a base.